Very little is known quantitatively about the elastic constants of an important class of liquid crystals formed by macromolecules in melts and solution. These moduli, representative of the forces between molecules, are fundamental in the establishment of the liquid crystal and determine its response and sensitivity to external perturbation, of chemical or physical origin. Lyotropic liquid crystals have been directly implicated in sickle cell disease where it is known that the formation of a liquid crystal organization within the red blood cells of polymers of the abnormal hemoglobulin, Hb-S, leads to the bizarre cellular shapes and elastic properties responsible for the clinical morbidity. Measurements of the twist elastic modulus, K22, of synthetic polypeptide solutions show that quite unlike the situation with small molecule counterparts, K22 is highly variable and dependent on controllable molecular parameters (e.g., molecular weight, size and shape, volume fraction of polymer, polymer-solvent interactions). In some cases the magnitude and trends of this constant can be accounted for on the basis of existing theory. Such data provide therefore a test of theory and thereby increase our understanding of effects at the microscopic level on macroscopic properties. We now seek to develop further procedures based on optical techniques known to work well in small molecule liquid crystals - to measure all three elastic constants K11 (i equals 1, 2 and 3) in polymer liquid crystals. Once these methods have been established and proven to provide consistent values of the K11 of large molecule systems of synthetic origin, the study will be directed to the determination of the elasticity of liquid crystal microfibrils of sickle cell hemoglobin. Effects of third component antisickling agents on the elasticity of the liquid crystal organization will then be investigated.